This invention relates generally to radiotelephone systems and equipment and more particularly to the method and apparatus used to communicate credit card information in a radiotelephone system in which a credit card is used to prepay for the radiotelephone call. This invention is related to U.S. patent application Nos. 057,402 (D'Avello et al.) and 057,479 (D'Avello et al.), each filed on the same date as the present invention and containing related subject matter.
Widespread mobile telephone service such as that afforded by cellular mobile telephone systems enables large numbers of users to have radiotelephone service in their vehicles. It has become desirable to extend mobile telephone service to other public transportation services such as taxicabs, bus, railroad, and rent-a-car services. Additionally, temporary fixed installation of radiotelephone service such as at trade shows or fairgrounds has become desirable. In so extending the service, those entities providing the service must address the problem of collecting payment for the telephone service provided Collection of coin and currency in pay phones placed on inter-urban trains has been known for a long time but adequate compensation for a long distance call or a call of long duration is often times difficult to collect in such a pay phone. The advent of credit cards with magnetic or other means of data storage has enabled the credit caller the opportunity to charge his calls to his credit card thereby assuring the telephone service provider payment for toll or metered telephone calls.
Generally, the procedure for enabling the credit card telephone is to have the potential user run his credit card through a magnetic stripe reader. This first step reads at least one "track" of the magnetic stripe (usually "track two") which includes, inter alia, identification of the card and expiration date. Further definition of magnetic stripe encoding may be found in ANSI X4.16-1983 "American National Standard for Financial Services - Financial Transaction Cards - Magnetic Stripe Encoding". A telephone call is then placed to the credit call provider and the track two information is read to the computer of the credit call provider. A check is then made of the card validity and expiration date and if no reason exists for denying service, a single telephone call is allowed. In this form, the operation is similar to that of an automatic teller machine (ATM). The single telephone call is dialled by the credit user to the computer (or telephone switch) of the credit call provider which subsequently redials the call to the public switched telephone network (PSTN). When the user terminates his call, the credit call provider senses the end of the call. The credit call provider can then calculate directly the duration of the call, any toll or metered charges, and any air time charges accumulated through the use of radiotelephone circuits. The disadvantage of this operation is that the credit call provider must maintain telephone switching equipment which must redial the user's call and must procure adequate input and output telephone trunks to carry the expected amount of telephone traffic.
Others have suggested that the credit call provider only needs to monitor the start and completion times of the user correlated to the particular mobile unit used in making the credit card call. In fact, a properly synchronized credit card mobile telephone system would need only the starting time (or the completion time) of each credit card use and the mobile telephone unit identification. Any calls made between the starting time of a first credit card authorization and the starting time of a second credit card authorization would be billed to the first credit card. Thus, the credit call provider would not have to maintain a telephone switch or lease a large number of input and output telephone trunks. It is not clear, however, that the equipment which interfaces with the credit card user can provide a telephone service which appears to the user to operate in a "normal" telephone mode, with each telephone call being made in a consistent and familiar manner.
In other credit call schemes, modifications have been suggested to the standard signalling protocol of the radiotelephone system which create a non-standard system. Further, if a standard system of signalling is maintained, it is desirable that a credit card data transmission technique be employed which correctly transmits the credit card information error free.